Aug 7, 2014 11:20 PM

Hello guys, I am currenty involved in a project wherein the final product will be wearable, light weight and should be pocket sized, or atleast can be put in a backpack. I have a little experience with PCB designing but not with the eclosure design and know nothing about the process. I am creating the layout now, and my question is, should the enclosure design work around the pcb layout? Or would it be better to work with the enclosure first and work the design of the pcb and components around that?

Do you have any companies that you could suggest? Or any other advice you can offer is highly appreciated. Thanks!

John, I think I would start with what I wanted the product to look like- then move to the PCB design, keeping in mind the desired finished product. Then design the enclosure. I call that a top down aproach to design- start with the grand idea, then add detail to the sub components.

I have a 3d printer and I am in the business of prototyping. Call me if you wish- Nine 4 One -Nine 8 One- 3613

John: I am just a "beginner" in this kind of stuff as I have been designing both the enclosures and PCB's for various devices/gadgets/products/projects for only 30-years!!! My design work has ranged from aerospace/avionics for both commercial and private aircraft (mostly BOEING 737's), DoD/Defense/Security projects for the CIA, DoD, FBI, NASA, NRO (who???), NSA and The Department of Homelad Security for a variety of "covert intelligence-gathering, surveillance and/or tracking operations" projects, various instrumentation for the "medical electronics industry" (cancer diagnostics, infectious-disease diagnostics, (similar to your project) a shirt-pocket sized microprocessor-based blood analyzer, etc., etc., developed the prototypes of what is now called "HD Digital Radio Broadcasting" and on and on!!!

Each project always has its own set of requirements and/or priorities which will dictate how the "chicken or egg" scenario will play out. I have had the experience of both ways plenty of times and there is NO "right way"!!! Whatever your circumstances dictate.

In your case, I would go with the enclosure first in order to meet whatever size constraints may exist, then I would design the PCB's. About 18-years ago I was brought in as a "Consultant" to a telecom company to design a new wireless product and when I got there, their engineers had already designed and committed to a specific custom-manufactured battery-pack. So.....that ended up being my starting point. I first designed their plastic enclosure to meet their mechanical physical requirements around the battery-pack and then I designed the required PCB's to fit within the enclosure, which also required matching up the PCB mounting holes to the enclosure mounting bosses. Can you imagine what "could" have happened if I had designed the PCB's first and then later find out that where I had placed a PCB mounting hole may not have been physically possible within the plastic enclosure? YIPES!!!

In your case.....there are plenty of "off-the-shelf" small plastic enclosures available from a long list of vendors. Low-cost, too!!! Some of these small enclosures even have LCD-display windows built into them and they look great!!! Since these manufacturers freely distribute CAD-drawings (either in AutoCAD, SolidWorks or "neutral" data-format files) or a set of PDF files to download, you can easily obtain all of the mechanical detail information in order to properly layout your PCB. Whatever floats your boat!!! If you would like some of the names of these vendors and/or to discuss your project, just contact me, OK???

If you wish to contact me, you can call me at: Three Zero One - Seven Three Nine - One Four Five Zero or via e-mail at: midnight_blue_designs AT YaH00 D0T c0m

I bought a Makerbot 3D printer about a year ago and it changed a lot about how I designed. Having immediate access to just about any plastic part you can think of lets you think outside the box. In your case it lets you think inside the box :-)

You can download a free copy of Autodesk 123D Design for the 3D CAD, then send your designs off to iMaterialise or any other printing service and get the printed design back in a few days for not much money. Or, chances are you can find someone that has a Makerbot or similar machine to run the part for you. Heck, if its simple I'll run it off for you. Message me back.

The 123D software is pretty good for free. My 12-year-old son snuck onto my workstation and taught himself the whole system in a day and printed out a set of passable Christmas ornamanets, so its not a huge effort to learn.

If you get to larger quantities (ie production) I get plastics CNC machined overseas and go straight to injection mold from there.

I would like to throw my biased opinion in here. Your design priorities should play a major part in your design process. For example, if the end size/shape is the main priority, then the case design is key followed by can you fit the electronics in it. The later than likely forces dealing with the economics of making it small. This can go to the extreme with custom System On Chip (SoC) designs that require million piece volumes to cover the development.

The more likely design scenario can be demonstrated by trends in 3D displays which vary from Oculus Rift to 3D glasses. There you see adaptations of existing technologies trying to accomplish the apparent ultimate goal of a Star Trek Holodeck.

For me I find it more productive to start with the electronics design based on what you can get in parts especially if you are green when it comes to overall design. If you already have a clear path to making the electronics do what you want you are more than half way there. Building a functional demonstrator of this has significant practical and psychological benefits. Rectangular cabinets come in a large array of sizes so your case should not be the initial constraint.

Most good designs are very iterative. You learn a great deal along the way. As you layout a board design you get a very good sense of the limitations of the costs, available parts, and how small you could potentially make it. Can you do it in 2 layers? How much space savings will a 4 layer, 6 layer, etc. buy me. Do I have signal constraints that demand 4 layer, 6 layer, etc. construction? More layers mean more money. BGA devices, while small, if the pad to pad spacing is too close, demand laser drilled vias that dramatically drive up costs. You can toaster oven assemble to lower apparent proto costs, but a BGA device will cost you more if you have an outside assembly house build up your board than a board that uses QFN parts.

There is also the issue of bringing up a new board design. I like to build a section of a board, test it, then build the next, so on. Trying to build the entire board at once never fails to bite me.

By the time you have built a functional demonstrator of your electronics you will have a very good idea of how small you could make it based on what you learned doing board No. 1. Then I would focus on the case. For board one, place connectors as needed. If you think you can use edge connectors to go to a front panel than do that and design the case around that. IF your are green to a new design, I would not make accomodating a case design be yet another thing to worry about even if you have been designing for years.

In your case, I would go with the enclosure first in order to meet whatever size constraints may exist, then I would design the PCB's. About 18-years ago I was brought in as a "Consultant" to a telecom company to design a new wireless product and when I got there,